1. Field of the Invention
The present invention relates to liquid heating cookers such as fryers and noodle boilers in which a heating medium such as cooking oil or water that has been filled into a vat is heated by a burner so as to cook foods such as French fries or noodles.
2. Description of the Related Art
Conventionally, fryers such as a fryer 100 shown in FIG. 9 are known. The fryer is provided with a vat 110 into which cooking oil for deep frying foods, such as French fries and chicken is filled, and a pulse burner 120 for heating the oil within the vat 110. The vat 110 and the pulse burner 120 are contained within a main housing 101. In the pulse burner 120, a combustion exhaust system is made of a combustion chamber 123 provided within the vat 110 and in which pulse combustion is carried out, a tailpipe 124 that serves as a route for discharging high temperature combustion exhaust from the combustion chamber 123, a decoupler 125 provided on the downstream side of the tailpipe 124, and an exhaust duct 126 provided on the downstream side of the decoupler 125.
Also, a gas conduit 121 for supplying fuel gas to the combustion chamber 123 is provided below the main housing 101, and a blower 122 for delivering air for combustion to the combustion chamber 123 is provided on the bottom surface of the main housing 101.
The vat 110 is made by welding together a plurality of flat panels. As shown in FIG. 7, broadly divided the vat 110 is constituted by a bottom panel 111 that forms a horizontal bottom wall portion, a front panel 113 that is bent in a plurality of locations and forms a front wall portion, a rear panel 114 including a rear wall portion 114a that is formed vertically and opposes the front panel 113 and a bottom wall portion 114b that slopes downward from the rear wall portion 114a toward the front, and left and right panels 115 and 116, respectively, that include vertical side wall portions and are opposed to one another. FIG. 8 shows the vat 110 after it has been welded together. The welding lines (welded portions) are illustrated by the thick solid lines in FIG. 8.
However, since the combustion chamber 123 and the tailpipe 124 are provided with the vat 110 in the fryer 100. Food residue generated from the foods during cooking sticks to the surface of the combustion chamber 123 and the tailpipe 124. Consequently it is not easily reached with cleaning things or with one's hand, which makes cleanup very difficult.
On the other hand, the following problems arise when a burner is used to heat the oil from outside the vat 110.
In a fryer that is used intermittently, the heat exchange surface of the vat 110, which is in contact with the approximately 1000° C. combustion gas and is where the exchange of heat takes place, is subject to repeated thermal expansion and contraction due to repeated heating and non-heating during fryer use. Consequently, as shown in FIG. 6, the corner areas of the heat exchange surface are compressed due to thermal expansion of the panels and are pulled due to contraction during cooling. Stress is thus easily concentrated in these corner areas.
Additionally, the composition and the thickness at the welded portions are not uniform, making the welded portions weaker than the non-welded portions. Moreover, the vat 110 is formed by combining flat panels to one another and welding, which means that the welded portions are located in the corner portions of the panels. As a result, the vat 110 is easily cracked due to the contraction and expansion of the panel.
The liquid heating cooker of the present invention solves the foregoing problems, and it is an object thereof to prevent cracking of the vat and increase its durability.